Low income or poverty is related to lower effortful control, which is important in the development of adaptive functioning and adjustment problems. Effortful control refers to attentional and inhibitory control mechanisms and shows a sharp developmental increase in the preschool years. However, rates and patterns of growth have not been examined extensively. Nor is there a good understanding about how the development of effortful control relates to the development of children's adjustment. Further, little is known about how sociodemographic risk might impact the development of effortful control. Low income or poverty might divert the development of effortful control during the key period of 3- to 6-years when it is developing dramatically. Low income might result in numerous family disruptions, including more negative events, residential instability, maternal depression, family conflict and disorganization. In turn, these might lead to greater stress reactivity and parenting problems that might mediate the effects of low income. We will investigate a process model of the effects of low income on effortful control in a community sample of 347 typically developing 3-year-olds. The sample will oversample risk with 1/3 families in poverty, 1/3 lower-income families, and 1/3 middle- to upper-income families. Using a growth design, we test whether the effects of low income on effortful control are mediated by family disruptions, stress reactivity and parenting. In turn, effortful control is expected to predict developing social competence and adjustment problems. This study is innovative in its use of a process model of the effects of low income, developmental design, and inclusion of behavioral, physiological, and neuropsychological measures. Children will be assessed 4 times. Assessments will include neuropsychological assessment of effortful control, physiological assessment of stress reactivity, observations of parenting, parents'report of family disruptions, and parents'and teachers'report of child adjustment. Latent growth curve analyses will be used to examine: 1) growth trajectories of effortful control;2) the role of low income in children's developing effortful control;3) whether family disruptions, stress reactivity, and parenting account for the effects of low income on effortful control;4) the relation between growth in effortful control and changes in adjustment;and 5) effortful control as a predictor of children's social competence and adjustment problems above the effects of low income and family disruptions. This project can inform interventions aimed at promoting positive adjustment in children in low-income contexts.